1. Field of the Invention
This invention relates to zig zag sewing machines in general, and in particular to machines having the capability of producing buttonholes of various sizes from stitch pattern information stored in an electronic memory.
2. Description of the Prior Art
Many different types of automatic buttonhole mechanisms are presently in use on sewing machines. One form of buttonhole mechanism gauges the length of buttonhole to be sewn on the basis of a switch having mechanical contacting elements whose spacing are varied according to the size of the button to be accommodated. Still other buttonhole mechanisms are controlled by wheels which engage and are driven by the fabric and which have optical sensors for determining the length of travel of the wheel. There are also known buttonhole mechanisms which are controlled by conductive marks which may be placed on the fabric in the location at which it is desired to start and terminate the buttonhole.
Recent developments in the sewing machine art have produced sewing machines in which stitch pattern information may be stored in and retrieved from an electronic memory. Such machines have a wide range of capabilities, limited only by the ability of the machine to retrieve stitch pattern information and apply it to the sewing instrumentalities.
One problem with prior known buttonhole mechanisms is that they are susceptible to faulty operation when their actuation is dependent on placing marks on the fabric.
Another problem is that the mechanisms are not fully compatible with electronic sewing machines having stitch pattern information stored in an electronic memory.
Still another problem is that some buttonhole mechanisms are susceptible to false operation due to the operator manipulating the fabric in the vicinity of the presser bar.